2 7 8 



Society Proceedings (122). 



suppresses in the hen and in the Sebright male the character- 

 istic cock-feathering. 



This view seems highly probable, although not, to our knowl- 

 edge, completely demonstrated as yet. However, if it could be 

 shown that as a consequence of thyroid feeding the lutear inter- 

 stitial tissue had increased in our hen-feathered male birds, the 

 fact would contribute strong support from a new direction. 

 Our preparations, however, indicate no such hypertrophy. There 

 seems to be little doubt of the complete or nearly complete absence 

 of lutear cells from the normal testis of R. I. R. cockerels at the 

 age of ten to fifteen weeks. The same appears to be true of the 

 thyroid-fed birds, but we are not so confident of the facts in this 

 case because of poor fixation of the tissues. New preparations 

 from experiments now in progress will probably clarify the 

 situation. 



The following series, however, adds some significance to the 

 lutear tissue in the present connection. 



1. In R. I. R. cockerels, ten to fifteen weeks of age, lutear 

 cells appear to be entirely lacking, and these birds fail entirely to 

 to develop tail coverts of the female type. 



2. In White Leghorn cockerels of the same age, lutear cells 

 are present and tail coverts of the female type are present also. 

 In W. L. adult males, however, these cells are lacking, as in adult 

 R. I. R. and correlated with their absence, the full male plumage 

 is present. 



3. In Sebright males, hen-feathering and lutear cells are present 

 together in young cockerel and in adult as well. 



R. I. R. males do not pass through a juvenal plumage, at 

 least so far as tail coverts are concerned. This is a rather ex- 

 ceptional fact, contrasting sharply with what we have found to 

 be true of the White Leghorn cockerel, and the Sebright, both 

 cockerel and adult. Juvenal plumage would thus appear to be 

 determined, not by age, but by cells whose presence, regardless 

 of age or of sex. leads always to plumage of one type. According 

 to this view, juvenal plumage is female plumage, and female, 

 juvenal — or neither, as in the Sebright adult male. This problem 

 has large implications, consideration of which would carry us 

 outside the proper limits of this paper. 



